Bibcode
Zapiór, M.; Schmieder, B.; Mein, P.; Mein, N.; Labrosse, N.; Luna, M.
Bibliographical reference
Astronomy and Astrophysics, Volume 623, id.A144, 10 pp.
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3
2019
Journal
Citations
6
Refereed citations
6
Description
Context. In previous work, we studied a prominence which appeared like a
tornado in a movie made from 193 Å filtergrams obtained with the
Atmospheric Imaging Assembly (AIA) imager aboard the Solar Dynamics
Observatory (SDO). The observations in Hα obtained simultaneously
during two consecutive sequences of one hour with the Multi-channel
Subtractive Double Pass Spectrograph (MSDP) operating at the solar tower
in Meudon showed that the cool plasma inside the tornado was not
rotating around its vertical axis. Furthermore, the evolution of the
Dopplershift pattern suggested the existence of oscillations of periods
close to the time-span of each sequence. Aims: The aim of the
present work is to assemble the two sequences of Hα observations
as a full data set lasting two hours to confirm the existence of
oscillations, and determine their nature. Methods: After having
coaligned the Doppler maps of the two sequences, we use a Scargle
periodogram analysis and cosine fitting to compute the periods and the
phase of the oscillations in the full data set. Results: Our
analysis confirms the existence of oscillations with periods between 40
and 80 min. In the Dopplershift maps, we identify large areas with
strong spectral power. In two of them, the oscillations of individual
pixels are in phase. However, in the top area of the prominence, the
phase is varying slowly, suggesting wave propagation.
Conclusions: We conclude that the prominence does not oscillate as a
whole structure but exhibits different areas with their own oscillation
periods and characteristics: standing or propagating waves. We discuss
the nature of the standing oscillations and the propagating waves. These
can be interpreted in terms of gravito-acoustic modes and magnetosonic
waves, respectively.
Movie attached to Fig. 2 is available at http://https://www.aanda.org
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